Sputnik, the first artificial satellite, was launched into space on a rocket by the Soviet Union in 1957. A year later, the USA followed suit with Explorer. Today there are more than 2,000 satellites in orbit around the Earth, used mainly for telephony, television, radio and digital data transmission. A large number are also used for geoscientific research and meteorology. Great Inventions explains the technology without which modern communication and many of the amenities we now take for granted would not be possible.